A Nudibranch

Obviously..

flickr photo-collage of nudibranches

Nudibranch on Wikipedia

Nudi-pixel: an online resource for nudibranch and sea slug identification using photographs

The word "nudibranch" comes from Latin nudus meaning "naked", and Greek brankhia meaning "gills". The name is appropriate since the dorids (infraclass Anthobranchia) breathe through a branchial plume of bushy extremities on their back, rather than using gills. By contrast, on the back of the aeolids in infraclass Cladobranchia there are brightly colored sets of tentacles called cerata.

Nudibranchs have cephalic (head) tentacles, which are sensitive to touch, taste, and smell. Club-shaped rhinophores detect the odors.

They are hermaphroditic, but can rarely fertilize themselves.

From: Wikipedia

I love Nudibranches!!